Figure 7-16 Air Quality Index for 169 U.S. Cities: 1990 and 2014
Average Number of Days per Year
| Good | Moderate | Unhealthy for Sensitive Groups | Unhealthy | Very Unhealthy | |
|---|---|---|---|---|---|
| 1990 | 192.0 | 106.0 | 53.4 | 11.9 | 1.7 |
| 2014 | 241.2 | 114.5 | 8.1 | 1.1 | 0.2 |
NOTES: Based on number of days in the year in which an AQI mesasurement was reported from any monitoring site in the county or Metropolican Staistical Area to the Air Quality Statistics database.
# Days Good: number of days in the year having an AQI value 0-50
# Days Moderate: number of days in the year having an AQI value 51-100
# Days Unhealthy for Sensitve Groups: number of days in the year having an AQI value 101-150
# Days Unhealthy: number of days in the year having an AQI value 151-200
# Days Very Unhealthy: number of days in the year having an AQI value greater than 201. This includes the AQI categories very unhealthy and hazardous.
SOURCE: U.S. Environmental Protection Agency, Air Quality Index Information. Available at http://www.epa.gov/airtrends/aqi_info.html as of August 2015.